The invention relates to a transmitting and a receiving device for a multipoint-to-point network, in particular a synchronous multipoint-to-point CDMA network, according to the preamble of claim 1 or the preamble of claim 3 and to a synchronization procedure for a multipoint-to-point network according to the preamble of claim 10.
Multipoint-to-point networks, in particular multipoint-to-point CDMA networks, can be used advantageously to implement back channels in interactive communications networks. Interactive communications networks are executed for example as so-called HFC networks or HFR networks; HFC=Hybrid Fibre Coax, HFR=Hybrid Fibre Radio. For the forward channel, a point-to-multipoint network is used, which contains an optical feeder line plus a coaxial cable network or radio network connecting thereto. For the back channel, use is being made increasingly of a multipoint-to-point network, e.g. a CDMA network, which can be formed optically, electrically or as a radio network as well as in mixed forms; CDMA=Code Division Multiple Access.
In a synchronous CDMA network with an exchange and a plurality of terminal stations, it is also the case that the terminal stations have to be synchronized to the clock pulse (master clock) of the exchange in frequency and phase. The clock pulse of the exchange is transmitted via the forward channel to the terminal stations, which each execute frequency synchronization by means of a PLL (Phase Locked Loop) and phase synchronization with phase correction to generate their individual clock pulse. To lock on, each terminal station transmits a synchronization signal via the back channel of the CDMA multipoint-to-point network to the exchange.
A synchronization procedure is already known in which synchronization signals are transmitted CDMA-coded to the exchange. Here the back channel is divided timewise into a first area, which is reserved for the transmission of information signals, and a second area, which is reserved for the transmission of synchronization signals. The second area is thus not available for information transmission, due to which the existing transmission capacity is not optimally utilized.